The use of ASIC's (Application specific Integrated Circuits) to implement the control of power supplies (e.g., a ballast) for lighting units is known in the art. ASIC's can perform the function(s) of a variety of discrete components on a single Integrated Component (IC). This is advantageous because the overall size of the power supply unit can be reduced. Also, in large volume applications, the cost of an ASIC is significantly less than the cost of discrete components that are required to perform the same function(s). This, in turn, reduces the overall cost and physical size of the power supply unit.
The ASIC's are typically designed to interface with specific components or stages in the power supply. The stages of the power supply may comprise one or more IC's and/or discrete elements. For example, FIG. 1 shows a power supply for a HID (High Intensity Discharge) lamp (not shown). The power supply 10 consists of three stages: a boost stage 11 for power factor correction, a down converter stage 12, and a full-bridge driver stage 13. The functions of these stages are well known in the art and are not described herein further. In this conventional device, three different ASIC's 14 are required to control the different stages of the power supply. Each of the ASIC's 14 are different and are designed to interface/control only with a particular stage.
Correspondingly, EPA 0 830 982 (Endo) shows a microcomputer and an ASIC being used to control a lighting circuit device for an automobile. This lighting circuit device may be used with multiple types of cars. Similar to the ASIC's 14, the ASIC used in the device of Endo is specifically designed for a particular hardware application. The ASIC, for example, can not be used to control another stage or hardware application of the lighting circuit device.
ASIC's may be either custom-made for the application or off-the-shelf components. Custom-made ASIC's are expensive and time-consuming to develop. Since the initial development cost for a custom-made ASIC may be high, they are typically only used in high volume applications, where the development costs can be spread-out in the price of all the units sold. In addition, a custom-made ASIC is typically designed to operate with a particular type of components/stages or a specific component/stage produced by a certain manufacturer. This prevents the ASIC's from being used with components/stages that perform the same type of function or components/stages from other manufacturers.
Off-the-shelf components typically require external components/hardware in order to use them in a specific application. The external components (e.g., other IC's and discrete electronic components) are necessary to interface the ASIC's to the particular stage. This, however, increases both the cost and size of the power supply. Another disadvantage is that when the off-the-self component is changed, the external components must be redesigned.
There thus exists in the art a need for a control system that takes advantage of all the benefits of ASIC's while allowing the same ASIC's to be used interchangeable with different system and power supply topologies.